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Alshareedah I, Borcherds WM, Cohen SR, Singh A, Posey AE, Farag M, Bremer A, Strout GW, Tomares DT, Pappu RV, Mittag T, Banerjee PR. Sequence-specific interactions determine viscoelasticity and aging dynamics of protein condensates. bioRxiv 2023:2023.04.06.535902. [PMID: 37066350 PMCID: PMC10104120 DOI: 10.1101/2023.04.06.535902] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Biomolecular condensates are viscoelastic materials. Here, we report results from investigations into molecular-scale determinants of sequence-encoded and age-dependent viscoelasticity of condensates formed by prion-like low-complexity domains (PLCDs). The terminally viscous forms of PLCD condensates are Maxwell fluids. Measured viscoelastic moduli of these condensates are reproducible using a Rouse-Zimm model that accounts for the network-like organization engendered by reversible physical crosslinks among PLCDs in the dense phase. Measurements and computations show that the strengths of aromatic inter-sticker interactions determine the sequence-specific amplitudes of elastic and viscous moduli as well as the timescales over which elastic properties dominate. PLCD condensates also undergo physical aging on sequence-specific timescales. This is driven by mutations to spacer residues that weaken the metastability of terminally viscous phases. The aging of PLCD condensates is accompanied by disorder-to-order transitions, leading to the formation of non-fibrillar, beta-sheet-containing, semi-crystalline, terminally elastic, Kelvin-Voigt solids. Our results suggest that sequence grammars, which refer to the identities of stickers versus spacers in PLCDs, have evolved to afford control over the metastabilities of terminally viscous fluid phases of condensates. This selection can, in some cases, render barriers for conversion from metastable fluids to globally stable solids to be insurmountable on functionally relevant timescales.
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2
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Lin AZ, Ruff KM, Dar F, Jalihal A, King MR, Lalmansingh JM, Posey AE, Erkamp NA, Seim I, Gladfelter AS, Pappu RV. Dynamical control enables the formation of demixed biomolecular condensates. Nat Commun 2023; 14:7678. [PMID: 37996438 PMCID: PMC10667521 DOI: 10.1038/s41467-023-43489-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 11/10/2023] [Indexed: 11/25/2023] Open
Abstract
Cellular matter can be organized into compositionally distinct biomolecular condensates. For example, in Ashbya gossypii, the RNA-binding protein Whi3 forms distinct condensates with different RNA molecules. Using criteria derived from a physical framework for explaining how compositionally distinct condensates can form spontaneously via thermodynamic considerations, we find that condensates in vitro form mainly via heterotypic interactions in binary mixtures of Whi3 and RNA. However, within these condensates, RNA molecules become dynamically arrested. As a result, in ternary systems, simultaneous additions of Whi3 and pairs of distinct RNA molecules lead to well-mixed condensates, whereas delayed addition of an RNA component results in compositional distinctness. Therefore, compositional identities of condensates can be achieved via dynamical control, being driven, at least partially, by the dynamical arrest of RNA molecules. Finally, we show that synchronizing the production of different RNAs leads to more well-mixed, as opposed to compositionally distinct condensates in vivo.
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Affiliation(s)
- Andrew Z Lin
- Division of Biology and Biomedical Sciences, Plant and Microbial Biosciences, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Kiersten M Ruff
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Furqan Dar
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Ameya Jalihal
- Department of Cell Biology, Duke University, Durham, NC, 27708, USA
| | - Matthew R King
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Jared M Lalmansingh
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Ammon E Posey
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Nadia A Erkamp
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
- Yusuf Hamied Department of Chemistry, Centre for Misfolding Diseases, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Ian Seim
- Department of Cell Biology, Duke University, Durham, NC, 27708, USA
| | - Amy S Gladfelter
- Department of Cell Biology, Duke University, Durham, NC, 27708, USA.
| | - Rohit V Pappu
- Division of Biology and Biomedical Sciences, Plant and Microbial Biosciences, Washington University in St. Louis, St. Louis, MO, 63130, USA.
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3
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Posey AE, Ross KA, Bagheri M, Lanum EN, Khan MA, Jennings CE, Harwig MC, Kennedy NW, Hilser VJ, Harden JL, Hill RB. The variable domain from dynamin-related protein 1 promotes liquid-liquid phase separation that enhances its interaction with cardiolipin-containing membranes. Protein Sci 2023; 32:e4787. [PMID: 37743569 PMCID: PMC10578129 DOI: 10.1002/pro.4787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 09/19/2023] [Accepted: 09/20/2023] [Indexed: 09/26/2023]
Abstract
Dynamins are an essential superfamily of mechanoenzymes that remodel membranes and often contain a "variable domain" important for regulation. For the mitochondrial fission dynamin, dynamin-related protein 1, a regulatory role for the variable domain (VD) is demonstrated by gain- and loss-of-function mutations, yet the basis for this is unclear. Here, the isolated VD is shown to be intrinsically disordered and undergo a cooperative transition in the stabilizing osmolyte trimethylamine N-oxide. However, the osmolyte-induced state is not folded and surprisingly appears as a condensed state. Other co-solutes including known molecular crowder Ficoll PM 70, also induce a condensed state. Fluorescence recovery after photobleaching experiments reveal this state to be liquid-like indicating the VD undergoes a liquid-liquid phase separation under crowding conditions. These crowding conditions also enhance binding to cardiolipin, a mitochondrial lipid, which appears to promote phase separation. Since dynamin-related protein 1 is found assembled into discrete punctate structures on the mitochondrial surface, the inference from the present work is that these structures might arise from a condensed state involving the VD that may enable rapid tuning of mechanoenzyme assembly necessary for fission.
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Affiliation(s)
- Ammon E. Posey
- Program in Molecular BiophysicsJohns Hopkins UniversityBaltimoreMarylandUSA
- Present address:
Department of Biomedical EngineeringWashington UniversitySt. LouisMissouriUSA
| | - Kyle A. Ross
- Department of BiochemistryMedical College of WisconsinMilwaukeeWisconsinUSA
| | - Mehran Bagheri
- Department of PhysicsUniversity of OttawaOttawaOntarioUSA
| | - Elizabeth N. Lanum
- Department of BiochemistryMedical College of WisconsinMilwaukeeWisconsinUSA
| | - Misha A. Khan
- Department of BiochemistryMedical College of WisconsinMilwaukeeWisconsinUSA
| | | | - Megan C. Harwig
- Department of BiochemistryMedical College of WisconsinMilwaukeeWisconsinUSA
| | - Nolan W. Kennedy
- Department of BiochemistryMedical College of WisconsinMilwaukeeWisconsinUSA
| | - Vincent J. Hilser
- Program in Molecular BiophysicsJohns Hopkins UniversityBaltimoreMarylandUSA
| | | | - R. Blake Hill
- Department of BiochemistryMedical College of WisconsinMilwaukeeWisconsinUSA
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4
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Posey AE, Bagheri M, Ross KA, Lanum EN, Khan MA, Jennings CM, Harwig MC, Kennedy NW, Hilser VJ, Harden JL, Hill RB. The variable domain from the mitochondrial fission mechanoenzyme Drp1 promotes liquid-liquid phase separation. bioRxiv 2023:2023.05.29.542732. [PMID: 37398258 PMCID: PMC10312466 DOI: 10.1101/2023.05.29.542732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Dynamins are an essential superfamily of mechanoenzymes that remodel membranes and often contain a "variable domain" (VD) important for regulation. For the mitochondrial fission dynamin, Drp1, a regulatory role for the VD is demonstrated by mutations that can elongate, or fragment, mitochondria. How the VD encodes inhibitory and stimulatory activity is unclear. Here, isolated VD is shown to be intrinsically disordered (ID) yet undergoes a cooperative transition in the stabilizing osmolyte TMAO. However, the TMAO stabilized state is not folded and surprisingly appears as a condensed state. Other co-solutes including known molecular crowder Ficoll PM 70, also induce a condensed state. Fluorescence recovery after photobleaching experiments reveal this state to be liquid-like indicating the VD undergoes a liquid-liquid phase separation under crowding conditions. These crowding conditions also enhance binding to cardiolipin, a mitochondrial lipid, raising the possibility that phase separation may enable rapid tuning of Drp1 assembly necessary for fission.
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5
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Fossat MJ, Posey AE, Pappu RV. Uncovering the Contributions of Charge Regulation to the Stability of Single Alpha Helices. Chemphyschem 2023; 24:e202200746. [PMID: 36599672 PMCID: PMC10734359 DOI: 10.1002/cphc.202200746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 12/07/2022] [Indexed: 01/06/2023]
Abstract
The single alpha helix (SAH) is a recurring motif in biology. The consensus sequence has a di-block architecture that includes repeats of four consecutive glutamate residues followed by four consecutive lysine residues. Measurements show that the overall helicity of sequences with consensus E4 K4 repeats is insensitive to a wide range of pH values. Here, we use the recently introduced q-canonical ensemble, which allows us to decouple measurements of charge state and conformation, to explain the observed insensitivity of SAH helicity to pH. We couple the outputs from separate measurements of charge and conformation with atomistic simulations to derive residue-specific quantifications of preferences for being in an alpha helix and for the ionizable residues to be charged vs. uncharged. We find a clear preference for accommodating uncharged Glu residues within internal positions of SAH-forming sequences. The stabilities of alpha helical conformations increase with the number of E4 K4 repeats and so do the numbers of accessible charge states that are compatible with forming conformations of high helical content. There is conformational buffering whereby charge state heterogeneity buffers against large-scale conformational changes thus making the overall helicity insensitive to large changes in pH. Further, the results clearly argue against a single, rod-like alpha helical conformation being the only or even dominant conformation in the ensembles of so-called SAH sequences.
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Affiliation(s)
| | | | - Rohit V. Pappu
- Department of Biomedical Engineering and the Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130
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6
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Pappu RV, Lin AZ, Ruff KM, Jalihal AP, Dar F, Posey AE, King MR, Lalmansingh JM, Gladfelter AS. Demixing of distinct ribonucleoprotein condensates is under dynamical control. Biophys J 2023; 122:443a. [PMID: 36784273 DOI: 10.1016/j.bpj.2022.11.2390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Rohit V Pappu
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Andrew Z Lin
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | | | - Ameya P Jalihal
- Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Furqan Dar
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Ammon E Posey
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Matthew R King
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Jared M Lalmansingh
- Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Amy S Gladfelter
- Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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7
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Posey AE, Pappu RV. Quantitative analysis of intracellular protein phase transitions. Biophys J 2023; 122:206a. [PMID: 36782999 DOI: 10.1016/j.bpj.2022.11.1239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Ammon E Posey
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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8
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Fossat MJ, Posey AE, Gupta N, Pappu RV. How does sequence influence charge regulation of disordered proteins? Biophys J 2023; 122:200a. [PMID: 36782971 DOI: 10.1016/j.bpj.2022.11.1211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Martin J Fossat
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Ammon E Posey
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Nikita Gupta
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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9
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Lin AZ, Ruff KM, Jalihal A, Dar F, King MR, Lalmansingh JM, Posey AE, Seim I, Gladfelter AS, Pappu RV. Dynamical control enables the formation of demixed biomolecular condensates. Res Sq 2023:rs.3.rs-2440278. [PMID: 36798397 PMCID: PMC9934772 DOI: 10.21203/rs.3.rs-2440278/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Macromolecular phase separation underlies the regulated formation and dissolution of biomolecular condensates. What is unclear is how condensates of distinct and shared macromolecular compositions form and coexist within cellular milieus. Here, we use theory and computation to establish thermodynamic criteria that must be satisfied to achieve compositionally distinct condensates. We applied these criteria to an archetypal ribonucleoprotein condensate and discovered that demixing into distinct protein-RNA condensates cannot be the result of purely thermodynamic considerations. Instead, demixed, compositionally distinct condensates arise due to asynchronies in timescales that emerge from differences in long-lived protein-RNA and RNA-RNA crosslinks. This type of dynamical control is also found to be active in live cells whereby asynchronous production of molecules is required for realizing demixed protein-RNA condensates. We find that interactions that exert dynamical control provide a versatile and generalizable way to influence the compositions of coexisting condensates in live cells.
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Affiliation(s)
- Andrew Z Lin
- Division of Biology and Biomedical Sciences, Plant and Microbial Biosciences, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Kiersten M Ruff
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Ameya Jalihal
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Furqan Dar
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Matthew R King
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Jared M Lalmansingh
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Ammon E Posey
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Ian Seim
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Amy S Gladfelter
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biomolecular Condensates, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
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10
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Lin AZ, Ruff KM, Jalihal A, Dar F, King MR, Lalmansingh JM, Posey AE, Seim I, Gladfelter AS, Pappu RV. Dynamical control enables the formation of demixed biomolecular condensates. bioRxiv 2023:2023.01.04.522702. [PMID: 36711465 PMCID: PMC9881950 DOI: 10.1101/2023.01.04.522702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Macromolecular phase separation underlies the regulated formation and dissolution of biomolecular condensates. What is unclear is how condensates of distinct and shared macromolecular compositions form and coexist within cellular milieus. Here, we use theory and computation to establish thermodynamic criteria that must be satisfied to achieve compositionally distinct condensates. We applied these criteria to an archetypal ribonucleoprotein condensate and discovered that demixing into distinct protein-RNA condensates cannot be the result of purely thermodynamic considerations. Instead, demixed, compositionally distinct condensates arise due to asynchronies in timescales that emerge from differences in long-lived protein-RNA and RNA-RNA crosslinks. This type of dynamical control is also found to be active in live cells whereby asynchronous production of molecules is required for realizing demixed protein-RNA condensates. We find that interactions that exert dynamical control provide a versatile and generalizable way to influence the compositions of coexisting condensates in live cells.
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11
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Bremer A, Posey AE, Borgia MB, Borcherds WM, Farag M, Pappu RV, Mittag T. Quantifying Coexistence Concentrations in Multi-Component Phase-Separating Systems Using Analytical HPLC. Biomolecules 2022; 12:biom12101480. [PMID: 36291688 PMCID: PMC9599810 DOI: 10.3390/biom12101480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 09/30/2022] [Accepted: 10/03/2022] [Indexed: 11/28/2022] Open
Abstract
Over the last decade, evidence has accumulated to suggest that numerous instances of cellular compartmentalization can be explained by the phenomenon of phase separation. This is a process by which a macromolecular solution separates spontaneously into dense and dilute coexisting phases. Semi-quantitative, in vitro approaches for measuring phase boundaries have proven very useful in determining some key features of biomolecular condensates, but these methods often lack the precision necessary for generating quantitative models. Therefore, there is a clear need for techniques that allow quantitation of coexisting dilute and dense phase concentrations of phase-separating biomolecules, especially in systems with more than one type of macromolecule. Here, we report the design and deployment of analytical High-Performance Liquid Chromatography (HPLC) for in vitro separation and quantification of distinct biomolecules that allows us to measure dilute and dense phase concentrations needed to reconstruct coexistence curves in multicomponent mixtures. This approach is label-free, detects lower amounts of material than is accessible with classic UV-spectrophotometers, is applicable to a broad range of macromolecules of interest, is a semi-high-throughput technique, and if needed, the macromolecules can be recovered for further use. The approach promises to provide quantitative insights into the balance of homotypic and heterotypic interactions in multicomponent phase-separating systems.
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Affiliation(s)
- Anne Bremer
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Ammon E. Posey
- Department of Biomedical Engineering, Center for Biomolecular Condensates (CBC), James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Madeleine B. Borgia
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Wade M. Borcherds
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Mina Farag
- Department of Biomedical Engineering, Center for Biomolecular Condensates (CBC), James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Rohit V. Pappu
- Department of Biomedical Engineering, Center for Biomolecular Condensates (CBC), James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
- Correspondence: (R.V.P.); (T.M.)
| | - Tanja Mittag
- Department of Structural Biology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
- Correspondence: (R.V.P.); (T.M.)
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Seim I, Posey AE, Snead WT, Stormo BM, Klotsa D, Pappu RV, Gladfelter AS. Dilute phase oligomerization can oppose phase separation and modulate material properties of a ribonucleoprotein condensate. Proc Natl Acad Sci U S A 2022; 119:e2120799119. [PMID: 35333653 PMCID: PMC9060498 DOI: 10.1073/pnas.2120799119] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 02/16/2022] [Indexed: 01/02/2023] Open
Abstract
SignificanceA large subclass of biomolecular condensates are linked to RNA regulation and are known as ribonucleoprotein (RNP) bodies. While extensive work has identified driving forces for biomolecular condensate formation, relatively little is known about forces that oppose assembly. Here, using a fungal RNP protein, Whi3, we show that a portion of its intrinsically disordered, glutamine-rich region modulates phase separation by forming transient alpha helical structures that promote the assembly of dilute phase oligomers. These oligomers detour Whi3 proteins from condensates, thereby impacting the driving forces for phase separation, the protein-to-RNA ratio in condensates, and the material properties of condensates. Our findings show how nanoscale conformational and oligomerization equilibria can influence mesoscale phase equilibria.
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Affiliation(s)
- Ian Seim
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Ammon E. Posey
- Department of Biomedical Engineering, Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130
| | - Wilton T. Snead
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Benjamin M. Stormo
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Daphne Klotsa
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Rohit V. Pappu
- Department of Biomedical Engineering, Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130
| | - Amy S. Gladfelter
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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13
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Posey AE, Fossat MJ, Pappu RV. Heterogeneous distributions of charge states determine the apparent net charge of intrinsically disordered proteins. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.1732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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14
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Hill B, Posey AE, BAGHERI MEHRAN, Harwig MC, Kennedy NW, Hilser VJ, Harden JL. The variable domain from the mitochondrial fission mechanoenzyme Drp1 promotes liquid-liquid phase separation. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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15
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Fossat MJ, Posey AE, Pappu RV. Quantifying charge state heterogeneity for proteins with multiple ionizable residues. Biophys J 2021; 120:5438-5453. [PMID: 34826385 PMCID: PMC8715249 DOI: 10.1016/j.bpj.2021.11.2886] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 11/03/2021] [Accepted: 11/19/2021] [Indexed: 01/07/2023] Open
Abstract
Ionizable residues can release and take up protons and this has an influence on protein structure and function. The extent of protonation is linked to the overall pH of the solution and the local environments of ionizable residues. Binding or unbinding of a single proton generates a distinct charge microstate defined by a specific pattern of charges. Accordingly, the overall partition function is a sum over all charge microstates and Boltzmann weights of all conformations associated with each of the charge microstates. This ensemble-of-ensembles description recast as a q-canonical ensemble allows us to analyze and interpret potentiometric titrations that provide information regarding net charge as a function of pH. In the q-canonical ensemble, charge microstates are grouped into mesostates where each mesostate is a collection of microstates of the same net charge. Here, we show that leveraging the structure of the q-canonical ensemble allows us to decouple contributions of net proton binding and release from proton arrangement and conformational considerations. Through application of the q-canonical formalism to analyze potentiometric measurements of net charge in proteins with repetitive patterns of Lys and Glu residues, we determine the underlying mesostate pKa values and, more importantly, we estimate relative mesostate populations as a function of pH. This is a strength of using the q-canonical approach that cannot be replicated using purely site-specific analyses. Overall, our work shows how measurements of charge equilibria, decoupled from measurements of conformational equilibria, and analyzed using the framework of the q-canonical ensemble, provide protein-specific quantitative descriptions of pH-dependent populations of mesostates. This method is of direct relevance for measuring and understanding how different charge states contribute to conformational, binding, and phase equilibria of proteins.
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Affiliation(s)
- Martin J Fossat
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri
| | - Ammon E Posey
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri.
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Abstract
Glycine-rich regions feature prominently in intrinsically disordered regions (IDRs) of proteins that drive phase separation and the regulated formation of membraneless biomolecular condensates. Interestingly, the Gly-rich IDRs seldom feature poly-Gly tracts. The protein fused in sarcoma (FUS) is an exception. This protein includes two 10-residue poly-Gly tracts within the prion-like domain (PLD) and at the interface between the PLD and the RNA binding domain. Poly-Gly tracts are known to be highly insoluble, being potent drivers of self-assembly into solid-like fibrils. Given that the internal concentrations of FUS and FUS-like molecules cross the high micromolar and even millimolar range within condensates, we reasoned that the intrinsic insolubility of poly-Gly tracts might be germane to emergent fluid-to-solid transitions within condensates. To assess this possibility, we characterized the concentration-dependent self-assembly for three non-overlapping 25-residue Gly-rich peptides derived from FUS. Two of the three peptides feature 10-residue poly-Gly tracts. These peptides form either long fibrils based on twisted ribbon-like structures or self-supporting gels based on physical cross-links of fibrils. Conversely, the peptide with similar Gly contents but lacking a poly-Gly tract does not form fibrils or gels. Instead, it remains soluble across a wide range of concentrations. Our findings highlight the ability of poly-Gly tracts within IDRs that drive phase separation to undergo self-assembly. We propose that these tracts are likely to contribute to nucleation of fibrillar solids within dense condensates formed by FUS.
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Affiliation(s)
- Mrityunjoy Kar
- Max Planck Institute of Cell Biology and Genetics (MPI-CBG), 01307 Dresden, Germany
| | - Ammon E. Posey
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Furqan Dar
- Department of Physics, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Anthony A. Hyman
- Max Planck Institute of Cell Biology and Genetics (MPI-CBG), 01307 Dresden, Germany
| | - Rohit V. Pappu
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
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17
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Posey AE, Ruff KM, Lalmansingh JM, Kandola TS, Lange JJ, Halfmann R, Pappu RV. Mechanistic Inferences From Analysis of Measurements of Protein Phase Transitions in Live Cells. J Mol Biol 2021; 433:166848. [PMID: 33539877 PMCID: PMC8561728 DOI: 10.1016/j.jmb.2021.166848] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 01/10/2021] [Accepted: 01/25/2021] [Indexed: 02/07/2023]
Abstract
The combination of phase separation and disorder-to-order transitions can give rise to ordered, semi-crystalline fibrillar assemblies that underlie prion phenomena namely, the non-Mendelian transfer of information across cells. Recently, a method known as Distributed Amphifluoric Förster Resonance Energy Transfer (DAmFRET) was developed to study the convolution of phase separation and disorder-to-order transitions in live cells. In this assay, a protein of interest is expressed to a broad range of concentrations and the acquisition of local density and order, measured by changes in FRET, is used to map phase transitions for different proteins. The high-throughput nature of this assay affords the promise of uncovering sequence-to-phase behavior relationships in live cells. Here, we report the development of a supervised method to obtain automated and accurate classifications of phase transitions quantified using the DAmFRET assay. Systems that we classify as undergoing two-state discontinuous transitions are consistent with prion-like behaviors, although the converse is not always true. We uncover well-established and surprising new sequence features that contribute to two-state phase behavior of prion-like domains. Additionally, our method enables quantitative, comparative assessments of sequence-specific driving forces for phase transitions in live cells. Finally, we demonstrate that a modest augmentation of DAmFRET measurements, specifically time-dependent protein expression profiles, can allow one to apply classical nucleation theory to extract sequence-specific lower bounds on the probability of nucleating ordered assemblies. Taken together, our approaches lead to a useful analysis pipeline that enables the extraction of mechanistic inferences regarding phase transitions in live cells.
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Affiliation(s)
- Ammon E Posey
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130, USA.
| | - Kiersten M Ruff
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Jared M Lalmansingh
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130, USA; Department of Physics, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Tejbir S Kandola
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; The Open University, Milton Keynes MK7 6AA, United Kingdom
| | - Jeffrey J Lange
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Randal Halfmann
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems, Washington University in St. Louis, St. Louis, MO 63130, USA.
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18
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Clover TM, O’Neill CL, Appavu R, Lokhande G, Gaharwar AK, Posey AE, White MA, Rudra JS. Self-Assembly of Block Heterochiral Peptides into Helical Tapes. J Am Chem Soc 2020; 142:19809-19813. [PMID: 32338879 PMCID: PMC7606833 DOI: 10.1021/jacs.9b09755] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Indexed: 02/07/2023]
Abstract
Patterned substitution of d-amino acids into the primary sequences of self-assembling peptides influences molecular-level packing and supramolecular morphology. We report that block heterochiral analogs of the model amphipathic peptide KFE8 (Ac-FKFEFKFE-NH2), composed of two FKFE repeat motifs with opposite chirality, assemble into helical tapes with dimensions greatly exceeding those of their fibrillar homochiral counterparts. At sufficient concentrations, these tapes form hydrogels with reduced storage moduli but retain the shear-thinning behavior and consistent mechanical recovery of the homochiral analogs. Varying the identity of charged residues (FRFEFRFE and FRFDFRFD) produced similarly sized nonhelical tapes, while a peptide with nonenantiomeric l- and d-blocks (FKFEFRFD) formed helical tapes closely resembling those of the heterochiral KFE8 analogs. A proposed energy-minimized model suggests that a kink at the interface between l- and d-blocks leads to the assembly of flat monolayers with nonidentical surfaces that display alternating stacks of hydrophobic and charged groups.
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Affiliation(s)
- Tara M. Clover
- Department
of Pharmacology and Toxicology, University
of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Conor L. O’Neill
- Department
of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Rajagopal Appavu
- Department
of Pharmacology and Toxicology, University
of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Giriraj Lokhande
- Department
of Biomedical Engineering, Texas A&M
University, College
Station, Texas 77843, United States
| | - Akhilesh K. Gaharwar
- Department
of Biomedical Engineering, Texas A&M
University, College
Station, Texas 77843, United States
| | - Ammon E. Posey
- Department
of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Center
for Science & Engineering of Living Systems (CSELS), McKelvey
School of Engineering, Washington University
in St. Louis, One Brookings
Drive, Campus Box 1097, St. Louis, Missouri 63130, United
States
| | - Mark A. White
- Sealy
Center for Structural Biology and Molecular Biophysics and Department
of Biochemistry and Molecular Biology, University
of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jai S. Rudra
- Department
of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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19
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Greig JA, Nguyen TA, Lee M, Holehouse AS, Posey AE, Pappu RV, Jedd G. Arginine-Enriched Mixed-Charge Domains Provide Cohesion for Nuclear Speckle Condensation. Mol Cell 2020; 77:1237-1250.e4. [PMID: 32048997 PMCID: PMC10715173 DOI: 10.1016/j.molcel.2020.01.025] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 12/04/2019] [Accepted: 01/23/2020] [Indexed: 12/29/2022]
Abstract
Low-complexity protein domains promote the formation of various biomolecular condensates. However, in many cases, the precise sequence features governing condensate formation and identity remain unclear. Here, we investigate the role of intrinsically disordered mixed-charge domains (MCDs) in nuclear speckle condensation. Proteins composed exclusively of arginine-aspartic acid dipeptide repeats undergo length-dependent condensation and speckle incorporation. Substituting arginine with lysine in synthetic and natural speckle-associated MCDs abolishes these activities, identifying a key role for multivalent contacts through arginine's guanidinium ion. MCDs can synergize with a speckle-associated RNA recognition motif to promote speckle specificity and residence. MCD behavior is tunable through net-charge: increasing negative charge abolishes condensation and speckle incorporation. Contrastingly, increasing positive charge through arginine leads to enhanced condensation, speckle enlargement, decreased splicing factor mobility, and defective mRNA export. Together, these results identify key sequence determinants of MCD-promoted speckle condensation and link the dynamic material properties of speckles with function in mRNA processing.
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Affiliation(s)
- Jamie A Greig
- Temasek Life Sciences Laboratory and Department of Biological Sciences, The National University of Singapore, Singapore 117604, Singapore
| | - Tu Anh Nguyen
- Temasek Life Sciences Laboratory and Department of Biological Sciences, The National University of Singapore, Singapore 117604, Singapore
| | - Michelle Lee
- Temasek Life Sciences Laboratory and Department of Biological Sciences, The National University of Singapore, Singapore 117604, Singapore
| | - Alex S Holehouse
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Ammon E Posey
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Gregory Jedd
- Temasek Life Sciences Laboratory and Department of Biological Sciences, The National University of Singapore, Singapore 117604, Singapore.
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20
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Lalmansingh JM, Posey AE, Kandola T, Halfmann R, Pappu RV. Basin Mapping Method for Extracting Comparative Assessments of Protein Phase Behavior from In Vivo Measurements. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.2949] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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21
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Hill B, Posey AE, Bagheri M, Harwig MC, Kennedy NW, Hilser VJ, Harden JL. The Variable Domain from the Mitochondrial Fission Mechanoenzyme Drp1 Promotes Liquid-Liquid Phase Separation. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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22
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Posey AE, Holehouse AS, Ruff KM, Pappu RV. Experimental and Theoretical Methods for Mapping Coexistence Curves of Phase-Separating Biological Macromolecules. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.1901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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23
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Ruff KM, Posey AE, Pappu RV. Modeling the Effects of Ligand Binding on the Phase Behavior of Aggregation-Prone Proteins. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.1100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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24
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Abstract
There is growing interest in the topic of intracellular phase transitions that lead to the formation of biologically regulated biomolecular condensates. These condensates are membraneless bodies formed by phase separation of key protein and nucleic acid molecules from the cytoplasmic or nucleoplasmic milieus. The drivers of phase separation are referred to as scaffolds whereas molecules that preferentially partition into condensates formed by scaffolds are known as clients. Recent advances have shown that it is possible to generate physical and functional facsimiles of many biomolecular condensates in vitro. This is achieved by titrating the concentration of key scaffold proteins and solution parameters such as salt concentration, pH, or temperature. The ability to reproduce phase separation in vitro allows one to compare the relationships between information encoded in the sequences of scaffold proteins and the driving forces for phase separation. Many scaffold proteins include intrinsically disordered regions whereas others are entirely disordered. Our focus is on comparative assessments of phase separation for different scaffold proteins, specifically intrinsically disordered linear multivalent proteins. We highlight the importance of coexistence curves known as binodals for quantifying phase behavior and comparing driving forces for sequence-specific phase separation. We describe the information accessible from full binodals and highlight different methods for-and challenges associated with-mapping binodals. In essence, we provide a wish list for in vitro characterization of phase separation of intrinsically disordered proteins. Fulfillment of this wish list through key advances in experiment, computation, and theory should bring us closer to being able to predict in vitro phase behavior for scaffold proteins and connect this to the functions and features of biomolecular condensates.
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Affiliation(s)
- Ammon E Posey
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO, United States
| | - Alex S Holehouse
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO, United States
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO, United States.
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25
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26
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Garai K, Posey AE, Li X, Buxbaum JN, Pappu RV. Inhibition of amyloid beta fibril formation by monomeric human transthyretin. Protein Sci 2018; 27:1252-1261. [PMID: 29498118 PMCID: PMC6032350 DOI: 10.1002/pro.3396] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 02/26/2018] [Accepted: 02/27/2018] [Indexed: 11/11/2022]
Abstract
Transthyretin (TTR) is a homotetrameric protein that is found in the plasma and cerebrospinal fluid. Dissociation of TTR tetramers sets off a downhill cascade of amyloid formation through polymerization of monomeric TTR. Interestingly, TTR has an additional, biologically relevant activity, which pertains to its ability to slow the progression of amyloid beta (Aβ) associated pathology in transgenic mice. In vitro, both TTR and a kinetically stable variant of monomeric TTR (M-TTR) inhibit the fibril formation of Aβ1-40/42 molecules. Published evidence suggests that tetrameric TTR binds preferentially to Aβ monomers, thus destabilizing fibril formation by depleting the pool of Aβ monomers from aggregating mixtures. Here, we investigate the effects of M-TTR on the in vitro aggregation of Aβ1-42 . Our data confirm previous observations that fibril formation of Aβ is suppressed in the presence of sub-stoichiometric amounts of M-TTR. Despite this, we find that sub-stoichiometric levels of M-TTR are not bona fide inhibitors of aggregation. Instead, they co-aggregate with Aβ to promote the formation of large, micron-scale insoluble, non-fibrillar amorphous deposits. Based on fluorescence correlation spectroscopy measurements, we find that M-TTR does not interact with monomeric Aβ. Two-color coincidence analysis of the fluorescence bursts of Aβ and M-TTR labeled with different fluorophores shows that M-TTR co-assembles with soluble Aβ aggregates and this appears to drive the co-aggregation into amorphous precipitates. Our results suggest that mimicking the co-aggregation activity with protein-based therapeutics might be a worthwhile strategy for rerouting amyloid beta peptides into inert, insoluble, and amorphous deposits.
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Affiliation(s)
- Kanchan Garai
- Department of Biomedical Engineering and Center for Biological Systems EngineeringWashington University in St. Louis, One Brookings Drive, Campus Box 1097St. LouisMissouri63130
- TIFR Centre for Interdisciplinary Sciences, 36/P Gopanpally Village, SerilingampallyHyderabad500019India
| | - Ammon E. Posey
- Department of Biomedical Engineering and Center for Biological Systems EngineeringWashington University in St. Louis, One Brookings Drive, Campus Box 1097St. LouisMissouri63130
| | - Xinyi Li
- Department of Molecular and Experimental MedicineThe Scripps Research Institute, 10550 North Torey Pines RoadLa JollaCalifornia92037
| | - Joel N. Buxbaum
- Department of Molecular and Experimental MedicineThe Scripps Research Institute, 10550 North Torey Pines RoadLa JollaCalifornia92037
| | - Rohit V. Pappu
- Department of Biomedical Engineering and Center for Biological Systems EngineeringWashington University in St. Louis, One Brookings Drive, Campus Box 1097St. LouisMissouri63130
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27
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Posey AE, Ruff KM, Harmon TS, Crick SL, Li A, Diamond MI, Pappu RV. Profilin reduces aggregation and phase separation of huntingtin N-terminal fragments by preferentially binding to soluble monomers and oligomers. J Biol Chem 2018; 293:3734-3746. [PMID: 29358329 PMCID: PMC5846159 DOI: 10.1074/jbc.ra117.000357] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 01/16/2018] [Indexed: 11/06/2022] Open
Abstract
Huntingtin N-terminal fragments (Htt-NTFs) with expanded polyglutamine tracts form a range of neurotoxic aggregates that are associated with Huntington's disease. Here, we show that aggregation of Htt-NTFs, irrespective of polyglutamine length, yields at least three phases (designated M, S, and F) that are delineated by sharp concentration thresholds and distinct aggregate sizes and morphologies. We found that monomers and oligomers make up the soluble M phase, ∼25-nm spheres dominate in the soluble S phase, and long, linear fibrils make up the insoluble F phase. Previous studies showed that profilin, an abundant cellular protein, reduces Htt-NTF aggregation and toxicity in cells. We confirm that profilin achieves its cellular effects through direct binding to the C-terminal proline-rich region of Htt-NTFs. We show that profilin preferentially binds to Htt-NTF M-phase species and destabilizes aggregation and phase separation by shifting the concentration boundaries for phase separation to higher values through a process known as polyphasic linkage. Our experiments, aided by coarse-grained computer simulations and theoretical analysis, suggest that preferential binding of profilin to the M-phase species of Htt-NTFs is enhanced through a combination of specific interactions between profilin and polyproline segments and auxiliary interactions between profilin and polyglutamine tracts. Polyphasic linkage may be a general strategy that cells utilize to regulate phase behavior of aggregation-prone proteins. Accordingly, detailed knowledge of phase behavior and an understanding of how ligands modulate phase boundaries may pave the way for developing new therapeutics against a variety of aggregation-prone proteins.
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Affiliation(s)
- Ammon E Posey
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Kiersten M Ruff
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Tyler S Harmon
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Scott L Crick
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Aimin Li
- the Department of Neurology, Washington University School of Medicine, St. Louis, Missouri 63108
| | - Marc I Diamond
- the Center for Alzheimer's and Neurodegenerative Diseases, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | - Rohit V Pappu
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130,
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28
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Posey AE, Kandola T, Pappu RV, Halfmann R. Advances in Quantitative Analysis of Intracellular Protein Phase Separation Kinetics and its Modulation by Cellular Interactions. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.3219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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29
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Fossat MJ, Harmon TS, Posey AE, Choi JM, Pappu RV. Increasing the Accuracy in All-Atom Simulations of Intrinsically Disordered Proteins based on the Absinth Model. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.2392] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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30
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Lee M, Lee EY, Lai GH, Kennedy NW, Posey AE, Xian W, Ferguson AL, Hill RB, Wong GCL. Molecular Motor Dnm1 Synergistically Induces Membrane Curvature To Facilitate Mitochondrial Fission. ACS Cent Sci 2017; 3:1156-1167. [PMID: 29202017 PMCID: PMC5704292 DOI: 10.1021/acscentsci.7b00338] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Indexed: 05/30/2023]
Abstract
Dnm1 and Fis1 are prototypical proteins that regulate yeast mitochondrial morphology by controlling fission, the dysregulation of which can result in developmental disorders and neurodegenerative diseases in humans. Loss of Dnm1 blocks the formation of fission complexes and leads to elongated mitochondria in the form of interconnected networks, while overproduction of Dnm1 results in excessive mitochondrial fragmentation. In the current model, Dnm1 is essentially a GTP hydrolysis-driven molecular motor that self-assembles into ring-like oligomeric structures that encircle and pinch the outer mitochondrial membrane at sites of fission. In this work, we use machine learning and synchrotron small-angle X-ray scattering (SAXS) to investigate whether the motor Dnm1 can synergistically facilitate mitochondrial fission by membrane remodeling. A support vector machine (SVM)-based classifier trained to detect sequences with membrane-restructuring activity identifies a helical Dnm1 domain capable of generating negative Gaussian curvature (NGC), the type of saddle-shaped local surface curvature found on scission necks during fission events. Furthermore, this domain is highly conserved in Dnm1 homologues with fission activity. Synchrotron SAXS measurements reveal that Dnm1 restructures membranes into phases rich in NGC, and is capable of inducing a fission neck with a diameter of 12.6 nm. Through in silico mutational analysis, we find that the helical Dnm1 domain is locally optimized for membrane curvature generation, and phylogenetic analysis suggests that dynamin superfamily proteins that are close relatives of human dynamin Dyn1 have evolved the capacity to restructure membranes via the induction of curvature mitochondrial fission. In addition, we observe that Fis1, an adaptor protein, is able to inhibit the pro-fission membrane activity of Dnm1, which points to the antagonistic roles of the two proteins in the regulation of mitochondrial fission.
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Affiliation(s)
- Michelle
W. Lee
- Department
of Bioengineering, Department of Chemistry & Biochemistry, and California NanoSystems
Institute, University of California, Los
Angeles, Los Angeles, California 90095, United States
| | - Ernest Y. Lee
- Department
of Bioengineering, Department of Chemistry & Biochemistry, and California NanoSystems
Institute, University of California, Los
Angeles, Los Angeles, California 90095, United States
| | - Ghee Hwee Lai
- Department
of Bioengineering, Department of Chemistry & Biochemistry, and California NanoSystems
Institute, University of California, Los
Angeles, Los Angeles, California 90095, United States
| | - Nolan W. Kennedy
- Department
of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, United States
| | - Ammon E. Posey
- Department
of Biomedical Engineering, Washington University
in St. Louis, St. Louis, Missouri 63130, United
States
| | - Wujing Xian
- Department
of Bioengineering, Department of Chemistry & Biochemistry, and California NanoSystems
Institute, University of California, Los
Angeles, Los Angeles, California 90095, United States
| | - Andrew L. Ferguson
- Department of Materials Science
and Engineering and Department of Chemical and Biomolecular
Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - R. Blake Hill
- Department
of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, United States
| | - Gerard C. L. Wong
- Department
of Bioengineering, Department of Chemistry & Biochemistry, and California NanoSystems
Institute, University of California, Los
Angeles, Los Angeles, California 90095, United States
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31
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Posey AE, Harmon TS, Pappu RV. Charge Neutralization, Not Salt Bridges, Stabilizes Alpha Helices in Repeating Blocks of Acidic and Basic Residues. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.1874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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32
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Harmon TS, Crabtree MD, Shammas SL, Posey AE, Clarke J, Pappu RV. GADIS: Algorithm for designing sequences to achieve target secondary structure profiles of intrinsically disordered proteins. Protein Eng Des Sel 2016; 29:339-46. [PMID: 27503953 DOI: 10.1093/protein/gzw034] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Accepted: 06/21/2016] [Indexed: 01/15/2023] Open
Abstract
Many intrinsically disordered proteins (IDPs) participate in coupled folding and binding reactions and form alpha helical structures in their bound complexes. Alanine, glycine, or proline scanning mutagenesis approaches are often used to dissect the contributions of intrinsic helicities to coupled folding and binding. These experiments can yield confounding results because the mutagenesis strategy changes the amino acid compositions of IDPs. Therefore, an important next step in mutagenesis-based approaches to mechanistic studies of coupled folding and binding is the design of sequences that satisfy three major constraints. These are (i) achieving a target intrinsic alpha helicity profile; (ii) fixing the positions of residues corresponding to the binding interface; and (iii) maintaining the native amino acid composition. Here, we report the development of a G: enetic A: lgorithm for D: esign of I: ntrinsic secondary S: tructure (GADIS) for designing sequences that satisfy the specified constraints. We describe the algorithm and present results to demonstrate the applicability of GADIS by designing sequence variants of the intrinsically disordered PUMA system that undergoes coupled folding and binding to Mcl-1. Our sequence designs span a range of intrinsic helicity profiles. The predicted variations in sequence-encoded mean helicities are tested against experimental measurements.
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Affiliation(s)
- Tyler S Harmon
- Department of Physics, Washington University in St. Louis, St. Louis, MO 63130, USA Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Michael D Crabtree
- Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW, Cambridge, UK
| | - Sarah L Shammas
- Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW, Cambridge, UK
| | - Ammon E Posey
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Jane Clarke
- Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW, Cambridge, UK
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
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Koppenol-Raab M, Harwig MC, Posey AE, Egner JM, MacKenzie KR, Hill RB. A Targeted Mutation Identified through pKa Measurements Indicates a Postrecruitment Role for Fis1 in Yeast Mitochondrial Fission. J Biol Chem 2016; 291:20329-44. [PMID: 27496949 DOI: 10.1074/jbc.m116.724005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Indexed: 12/25/2022] Open
Abstract
The tail-anchored protein Fis1 is implicated as a passive tether in yeast mitochondrial fission. We probed the functional role of Fis1 Glu-78, whose elevated side chain pKa suggests participation in protein interactions. Fis1 binds partners Mdv1 or Dnm1 tightly, but mutation E78A weakens Fis1 interaction with Mdv1, alters mitochondrial morphology, and abolishes fission in a growth assay. In fis1Δ rescue experiments, Fis1-E78A causes a novel localization pattern in which Dnm1 uniformly coats the mitochondria. By contrast, Fis1-E78A at lower expression levels recruits Dnm1 into mitochondrial punctate structures but fails to support normal fission. Thus, Fis1 makes multiple interactions that support Dnm1 puncta formation and may be essential after this step, supporting a revised model for assembly of the mitochondrial fission machinery. The insights gained by mutating a residue with a perturbed pKa suggest that side chain pKa values inferred from routine NMR sample pH optimization could provide useful leads for functional investigations.
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Affiliation(s)
| | - Megan Cleland Harwig
- the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, and
| | - Ammon E Posey
- From the Department of Biology and the Program in Molecular Biophysics, Johns Hopkins University, Baltimore, Maryland 21218
| | - John M Egner
- the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, and
| | - Kevin R MacKenzie
- the Department of Pathology, Baylor College of Medicine, Houston, Texas 77030
| | - R Blake Hill
- the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, and
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Posey AE, Ruff KM, Harmon TS, Holehouse AS, Pappu RV. Profilin Binding Modulates the Aggregation and Phase Separation of Huntingtin N-Terminal Fragments via Polyphasic Linkage. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Chang CR, Manlandro CM, Arnoult D, Stadler J, Posey AE, Hill RB, Blackstone C. A lethal de novo mutation in the middle domain of the dynamin-related GTPase Drp1 impairs higher order assembly and mitochondrial division. J Biol Chem 2010; 285:32494-503. [PMID: 20696759 DOI: 10.1074/jbc.m110.142430] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria dynamically fuse and divide within cells, and the proper balance of fusion and fission is necessary for normal mitochondrial function, morphology, and distribution. Drp1 is a dynamin-related GTPase required for mitochondrial fission in mammalian cells. It harbors four distinct domains: GTP-binding, middle, insert B, and GTPase effector. A lethal mutation (A395D) within the Drp1 middle domain was reported in a neonate with microcephaly, abnormal brain development, optic atrophy, and lactic acidemia (Waterham, H. R., Koster, J., van Roermund, C. W., Mooyer, P. A., Wanders, R. J., and Leonard, J. V. (2007) N. Engl. J. Med. 356, 1736-1741). Mitochondria within patient-derived fibroblasts were markedly elongated, but the molecular mechanisms underlying these findings were not demonstrated. Because the middle domain is particularly important for the self-assembly of some dynamin superfamily proteins, we tested the hypothesis that this A395D mutation, and two other middle domain mutations (G350D, G363D) were important for Drp1 tetramerization, higher order assembly, and function. Although tetramerization appeared largely intact, each of these mutations compromised higher order assembly and assembly-dependent stimulation of Drp1 GTPase activity. Moreover, mutant Drp1 proteins exhibited impaired localization to mitochondria, indicating that this higher order assembly is important for mitochondrial recruitment, retention, or both. Overexpression of these middle domain mutants markedly inhibited mitochondrial division in cells. Thus, the Drp1 A395D lethal defect likely resulted in impaired higher order assembly of Drp1 at mitochondria, leading to decreased fission, elongated mitochondria, and altered cellular distribution of mitochondria.
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Affiliation(s)
- Chuang-Rung Chang
- Institute of Biotechnology and Department of Life Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan
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Kim JW, Posey AE, Watt GD, Choi SH, Lillehei PT. Gold nanoshell assembly on a ferritin protein employed as a bio-template. J Nanosci Nanotechnol 2010; 10:1771-1777. [PMID: 20355572 DOI: 10.1166/jnn.2010.2078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Gold nanoshells around 26 nm in diameter with a 7 nm thick wall were fabricated in an aqueous solution using pre-reconstituted ferritin proteins as a removable bio-template. The synthesis of gold nanoshells was initiated by planting gold nanoparticle seeds in the hydrophilic three-fold channels of the ferritin protein. The process was facilitated by the energetically favorable gold-sulfur bonds formed at the cysteine residues lining these channels.
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Affiliation(s)
- Jae-Woo Kim
- National Institute of Aerospace, Hampton, VA 23666, USA
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